Comparison of Point of Care and Laboratory Glucose Analysis in Critically Ill Patients

ABSTRACT

By Teresita Lacara, RN, BSN, Caroline Domagtoy, RN, BSN, Donna Lickliter, RN,

Kathy Quattrocchi, RN, BSN, Lydia Snipes, RN, Joánne Kuszaj, RN, MSN, CCRN,

and MaryClare Prasnikar, RN, MSN, CCRN

Background Blood for point-of-care analysis of glucose levels is often obtained from different sources (fingerstick, arterial or central venous catheter).

Objectives To examine agreement between point-of-care and laboratory glucose values and to determine effects of hematocrit, serum carbon dioxide, and mean arterial pressure on the accuracy of point-of-care values.

Methods Point-of-care values were compared with laboratory values. In 49 critically ill patients, blood was obtained first from a catheter for laboratory testing and then from the catheter and via fingerstick for point-of-care testing. Bias, precision, and rootmean- square differences were calculated to quantify differences in values between the 2 methods. A t test was used to determine differences in values between each point-of-care blood source and the laboratory value. Multiple regression analysis was used to determine if serum level of carbon dioxide, hematocrit, and/or

mean arterial pressure significantly contributed to the difference in bias and precision for the point-of-care blood sources.

Results Mean laboratory glucose level was 135 (SEM 5.3, range 58-265) mg/dL. In point-of-care testing, bias ± precision and root-mean-square differences were 2.1 ± 12.3 and 12.35, respectively, for fingerstick blood and 0.6 ± 10.6 and 10.46 for catheter blood. Values for point-of-care and laboratory tests did not differ significantly. For catheter samples, hematocrit and serum carbon dioxide contributed significantly to difference scores between point-of-care and laboratory values (P < .001).

Conclusions Glucose values for point-of-care samples did not differ significantly from laboratory values. For catheter samples, hematocrit and serum carbon dioxide levels accounted for the difference between point-of-care and laboratory glucose

values. (American Journal of Critical Care. 2007;16:336-347)

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